Bioactive comparison of a borate, phosphate and silicate glass
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Christian Rüssel Otto-Schott-Institut, Universität Jena, Jena 07743, Germany
Delbert E. Day Materials Research Center, University of Missouri–Rolla, Rolla, Missouri 65409
Günter Völksch Otto-Schott-Institut, Universität Jena, Jena 07743, Germany (Received 6 June 2005; accepted 12 September 2005)
A borate glass, phosphate glass, and silicate glass were converted to hydroxyapatite (HA) by soaking the substrates in a solution of K2HPO4 with a pH value of 9.0 at 37 °C. The weight loss of the substrates was studied as a function of time. Unlike the silicate glasses, the reaction processes of the borate glasses and phosphate glasses were bulk dissolution. X-ray diffraction and scanning electron microscopy revealed an initially amorphous product that subsequently crystallized to HA. The data suggest good bioactive characteristics for the borate and phosphate glass and the potential use of them as a favorable template for bone-tissue formation.
I. INTRODUCTION
Nowadays, there is a growing trend to develop bioactive materials for use in the body to repair bone. These materials must promote a beneficial tissue response, encourage new tissue formation, and involve interactions of cells with the materials.1–4 Bioactive ceramics and glasses, including 45S5 Bioglass, apatite-wollastonite glass-ceramic, and so on, have been successfully used commercially. They have osteoconductive properties and thus are suitable for regeneration of bone tissue, for example in filling bone defects and treatment of benign bone tumors and bone loss due to periodontal diseases.5–8 In a body environment, these bioactive glass and glassceramics form an apatite layer on their surface resulting in chemical bond to bone tissue.9–11 It has been proposed that hydrated silica gel formed on the surface of these materials in the body plays an important role in forming the surface apatite layer. The silica gel acts not only as a chelating agent but is also flexible enough to supply the correct atomic distance required by the crystal structure of bone apatite.12–16 However, the long-term reaction to silica, both locally and systemically, is still unknown.17 a)
Address all correspondence to this author. Present address: Engineering Research Center for Biomedical Materials of Ministry of Education, East China University of Science and Technology, Shanghai 200237, P.R. China. e-mail: [email protected] DOI: 10.1557/JMR.2006.0025 J. Mater. Res., Vol. 21, No. 1, Jan 2006
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In previous work, some silicate-free borate and phosphate glasses were studied, and they are believed to be bioactive in the same sense as the traditional bioactive silica-based glasses.18,19 In this paper, the reactions of phosphate and borate glass with K2HPO4 solution were investigated and compared to 45S5 Bioglass. The processes of hydroxyapatite (HA) formation on the surface of glasses in K2HPO4 solution were studied. X-ray diffraction (XRD) was used to evaluate the crystallinity of HA formed on glasses. A scanning electron micros
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